1. Field of the Invention
The present invention relates, in general, to flat fluorescent lamps used as backlight units (BLU) in display devices, such as LCDs, and, more particularly, to a gas injection port structure of a flat fluorescent lamp (FFL), which is configured such that a gas injection port of the FFL is level with or lower than the height of a protruding channel provided on an upper plate of the FFL, thus minimizing the thickness of the FFL and accomplishing the recent trend of thinness of products having the FFLs.
2. Description of the Related Art
Generally, to produce a fluorescent lamp, first, a hollow glass body having a specific shape is provided by appropriately processing glass at a high temperature. Second, air is drawn out of the hollow glass body through a gas injection port so that the internal pressure of the glass body is reduced to form vacuum, and, thereafter, inert gas is injected into the vacuumized glass body through the gas injection port. After the first and second processes have been completed, the gas injection port is sealed. Conventional fluorescent lamps produced through the above-mentioned process may have various shapes, for example, linear shapes, specifically curved shapes and flat shapes. To allow the air to be drawn out of the hollow glass body of a fluorescent lamp to form a vacuum and the inert gas to be injected into the vacuumized glass body, a gas injection port is provided at each end of the glass body. Furthermore, an electrode may be provided at the gas injection port when necessary.
FIG. 1 is a perspective view illustrating the construction of a conventional flat fluorescent lamp (FFL) 10. FIG. 2 is a sectional view illustrating a gas injection port 14 of the FFL 10 of FIG. 1. As shown in the drawings, the conventional FFL 10 comprises a lower plate 11 having a flat shape, and an upper plate 12 having a protruding serpentine channel 13 and being integrated with the lower plate 11 into a single body. In the conventional FFL 10, the protruding serpentine channel 13 is formed as a continuous long channel having a serpentine shape, both ends of which are separated from each other.
As shown FIGS. 1 and 2, the serpentine channel 13 that forms the lamp part of the FFL 10 is provided with a vertical gas injection port 14 at each end thereof. The gas injection port 14 is directed upwards from each end of the serpentine channel 13 on the upper plate 12 so that the port 14 protrudes to a predetermined height. During a process of manufacturing the FFL 10, air is drawn out of the channel 13 through the gas injection ports 14 to form a vacuum in the channel 13, and, thereafter, inert gas is injected into the vacuumized channel 13 prior to sealing the gas injection ports 14 using a sealing material.
However, the gas injection ports 14 of the conventional FFL 10 are directed upwards from the opposite ends of the channel 13 as described above, thus undesirably increasing the thickness of the FFL 10. The above-mentioned increase in the thickness of the FFL 10 also thickens the display products, such as LCDs, produced using the FFLs 10.
In addition to the above-mentioned problem, the upward directed gas injection ports 14 may induce damage to the upper plate 12 during the processes of drawing air out of the channel 13, injecting inert gas into the channel 13, and sealing the ports 14 after the inert gas has been injected into the channel 13. Thus, the above-mentioned processes must be carefully executed, reducing work efficiency during the processes. Furthermore, to avoid damage to the gas injection ports 14 during the above-mentioned processes, the FFL 10 must be placed in a horizontal position from the start to the end of the processes, so that the FFL 10 requires a large working area.
In an effort to overcome the above-mentioned problems, another conventional FFL 20 having horizontal gas injection ports 24 as shown in FIGS. 3 through 5 has been proposed. As shown in the drawings, one or more horizontal gas injection ports 24 are provided on the FFL 20 at predetermined positions of a channel 23. Each of the gas injection ports 24 has a predetermined length and a throat having a semicircular cross-section, the sectional area of which is gradually reduced in a direction towards the channel 23. A gas injection hole 25 is formed through a lower plate 21 of the FFL 20 so that the hole 25 communicates with the interior of an associated gas injection port 24.
Furthermore, to draw air out of the channel 23 of an upper plate 22 of the FFL 20 and to inject inert gas into the channel 23 through the gas injection ports 24, a nozzle 30 is provided at the inlet of each gas injection hole 25 of the lower plate 21. The inside end of the nozzle 30 is provided with a flange 31 which has a diameter larger than the diameter of the gas injection hole 25, with a stopper 32 placed on the flange 31 restricting the undesired flow of sealing material 26 out of the gas injection port 24. Furthermore, an elastic sealing member 33 is interposed between the gas injection hole 25 and the flange 31 provided at the end of the nozzle 30, thus providing a desired seal at the junction of the gas injection hole 25 and the flange 31. Due to the gas injection ports 24 having the nozzles 30, the processes of drawing air out of the channel 23 and injecting inert gas into the vacuumized channel 23 can be efficiently executed.
The sealing material 26 is provided in each of the gas injection ports 20, with a passage 27 formed through the sealing material 26 in each of the gas injection ports 20. Thus, the gas injection ports 24 communicate with the channel 23 of the upper plate 22 through the passages 27. Due to the passages 27, the sealing materials 26 do not interfere with the flow of air or inert gas during the processes of drawing the air out of the channel 23 and injecting the inert gas into the channel 23. After the inert gas has been injected into the channel 23 through the gas injection ports 24, the sealing material 26 is fused using a heater H. Thus, the passage 27 in each of the gas injection ports 24 is closed, so that the channel 23 is completely isolated from the atmosphere.
As described above, each of the gas injection ports 24 of the conventional FFL 20 illustrated in FIGS. 3 through 5 must be provided with a nozzle 30 for drawing air out of the channel 23 and for injecting inert gas into the channel 23. Therefore, the FFL 20 is problematic in that it is difficult to produce the FFL 20. Furthermore, the gas injection ports 24 have a complex construction, causing difficulty and reducing work efficiency during the process of injecting the inert gas into the channel 23.